Watling Tyres in Catford quoted me £24 for the front.
That loose wheels, or ride in? I had 4 sets of tyres changed at Watling Dartford recently (top of East Hill) - was quoted and paid £20 per pair for loose wheels
Seems to be the same across the board at Watlings. When I was trackdaying a lot I used to get a pair changed on loose wheels regularly. It used to be ' oh, just give the fitter a drink' if you went at quite times. I used to give him a tenner and he was happy with that. Then about 2008 Watlings obviously realised it was something that the company could profit from so they started charging 20 quid. If we guess the fitter is on 10 quid per hour and changes 2 tyres in 15 mins he has earned 2.50 for the job and the company 17.50.
TBH, I still think 20 quid is cheap enough that I wouldnt bother trying to change tubeless tyres myself.
In fairness, 36 quid is cheap for ride in ride out near to home. If you quibble about that buy the stands,sockets etc and take the wheels off yourself. Or spend 5 quid in fuel riding further to save a couple of quid.
